The invention relates to an operating system for a part of a closing unit which part is to be operated externally, in particular for a tool carrier of a closing unit.
In the following, reference is made to a closing unit for a plastics processing machine with at least one mold carrier. It should be expressly noted, however, that the present invention is equally applicable for other externally operated parts of closing units. The tern “externally to be operated” denotes hereby that an opening and closing apparatus is not arranged within the closing unit but opening and closing of the closing unit is effected outside the closing unit.
Closing units of plastics processing machines, such as polyurethane installations, normally have two mold carriers which, for closing and opening of the closing unit, are movable toward one another (closing) or away from one another (opening). In this context, reference is made to German patent publication DE 101 52 392 which describes a closing unit for a plastics machine. The illustrated closing unit includes a lower mold carrier and an upper mold carrier which are each swingable about a common axis. During operation of the entire closing unit, the lower mold carrier is moved back and forth between two positions, namely a lower position in which mold elements are placed into the mold carrier or mold parts can be removed, and an upper position in which the closing unit is closed altogether to process a starting material in a predetermined manner. The upper mold carrier is also moved back and forth between two positions during operation of the entire closing unit, namely into an upper position in which the closing unit is open, and a lower position for shaping the introduced starting material.
In DE 101 52 392, the closing units themselves are fixedly disposed at one location, only the mold holders are swingably mounted.
It is, however, known, to arrange for example several closing units upon a rotary platform or turntable, with the individual closing units successively undergoing the same operating steps during operation of the turntable. For example, a starting material may be introduced, when the closing unit is open. At the same time, the starting material can be molded to shape in another closing unit. In still another closing unit, a finished molded part may be withdrawn at the same time. The use of such devices—likewise as in DE 101 52 392—requires operation, especially pivoting to open and to close, of the various parts of the closing unit in a predefined manner.
A method known per se involves the use of external actuators, whereby a cam roller is arranged upon an externally to-be-operated part of a closing unit, for example upon an upper mold carrier, for running, at least partly, on a rail structure and is opened or closed by a gripper member at particular positions. It is known to implement the gripper member, for example, in the form of a U profile, with the cam roller being able to move into the groove thereof. When the cam roller is received in the groove of the U profile, a movement of the upper mold carrier is possible by movement (pivoting, travel) of the U profile. Once the upper mold carrier has reached a particular position, it moves out again from the groove of the U profile and may roll subsequently for example on a further rail by means of the cam roller.
The use of such rigid profiles or rails for the gripper member has, however, the drawback of a relative movement between cam roller and rail, when all the closing units are operated. This leads to relatively high wear as a result of friction. Moreover, the gripper member must be precisely adjusted and moved to keep wear as small as possible.